MMRV Vaccine Ups Fever and Seizure Risk

Large study confirms previous preliminary findings in young children

By Beth Gilbert

HealthDay Reporter

TUESDAY, June 29 (HealthDay News) -- Measles-mumps-rubella-varicella (MMRV) vaccination is associated with an increased risk of fever and seizure in young children, above that already associated with measles-containing vaccines, according to research published online June 29 in Pediatrics, confirming preliminary evidence from a previous study.

In an analysis using Vaccine Safety Datalink data from 2000 to 2008, Nicola P. Klein, M.D., of the Kaiser Permanente Vaccine Study Center in Oakland, Calif., and colleagues evaluated seizure and fever visits among children aged 12 to 23 months after MMRV and separate MMR plus varicella vaccines. In a previous preliminary study, the researchers had found that the MMRV vaccine is linked to a two-fold increased risk of febrile seizures compared with separate MMR and varicella vaccines. The current study included data on twice as many vaccine recipients.

The researchers found that with all measles-containing vaccines, seizure and fever significantly clustered seven to 10 days after vaccination, but this was not the case after varicella vaccination alone. In addition, during days seven to 10 after vaccination, the seizure risk was higher after MMRV vaccination compared to after MMR plus varicella vaccination, with a relative risk of 1.98. The researchers determined that MMRV vaccination leads to one additional febrile seizure for every 2,300 doses given instead of MMR plus varicella vaccines.

"Providers who recommend MMRV should communicate to parents that it increases the risk of fever and seizure over that already associated with measles-containing vaccines," the authors write.

Two authors disclosed receiving research support from Merck & Co., Novartis, GlaxoSmithKline, Wyeth, and Sanofi-Pasteur.